Polyorganosiloxane compositions which cure to elastomeric materials at room temperature are well known. Such compositions can be obtained by mixing polydiorganosiloxanes having reactive groups, such as silanol groups, with silane crosslinking agents, for example, alkoxysilanes, acetoxysilanes, oximosilanes, or aminosilanes. Compositions comprising these ingredients can then be cured by exposure to atmospheric moisture at room temperature. Many of these compositions, however, evolve by-products during cure such as acetic acid and ketoximes which have unpleasant odors and may be corrosive. The use of other compositions which would not have these properties would therefore be beneficial.
One potential alternative is a "neutral cure" RTV composition which does not evolve these types of by-products. An example of a neutral cure RTV composition liberates alcohol during cure and comprises polydiorganosiloxanes having hydroxysilyl or alkoxysilyl chain terminations, an alkoxysilane and a titanium compound. When these compositions are made into sealants, different fillers are often added so that certain desired rheological properties may be obtained such as non-slump handling characteristics. Although desired rheological properties may be obtained, it has been observed that the addition of certain quantities of a silica filler to these compositions may affect the adhesive properties of the sealant to various substrates. Therefore, it would be beneficial to prepare a neutral cure composition having improved adhesive properties under these conditions.
The present inventors have unexpectedly determined that RTV compositions comprising polymers having hydroxysilyl or alkoxysilyl chain terminations, a titanium compound, an alkoxysilane, and a silica filler have improved adhesion to glass and ceramic materials when the titanium compound is present in only about 0.05 to 1.4 weight percent based on the total weight of the RTV composition and a sufficient amount of an aminofunctional alkoxysilane is added to provide a nitrogen concentration from about 0.01 to 2 weight percent based on the total weight of the RTV composition.
One objective of the present invention is to prepare a silica filled RTV composition having improved adhesion to glass and ceramic materials. Another objective of the present invention is to provide a method of adhering a silica filled RTV composition to glass or ceramic materials.